1. Field of the Invention
This invention relates to an acceleration detecting device which is a device to detect acceleration of an object and that is favorable for sensing the collision of a vehicle and causing the activation of passenger protection apparatus such as an airbag.
2. Related Art
Conventionally known devices mechanically assess acceleration information by a rotor with a weight center of gravity and an eccentric rotational center and output an external electrical signal by a contact which rotates integrally with the rotor, (as seen in Japanese Patent Application Laid-open No. Hei. 2-168525 Patent Gazette). In this case, a single function is assigned to each part: the rotor rotates due to acceleration, a spring urges the rotor to prevent operation at times other than acceleration action, and the contact relays an electrical signal output of the rotation of the rotor.
However, assigning a single function to every part causes the number of parts and mechanical connections to increase. Additionally, assurance of the spacing of contact points is structurally difficult, and so there exist problems of a lack of stability in quality, and an inability to make the acceleration detecting device compact and lightweight.
Additionally, in a case where an acceleration detecting device is applied in an airbag apparatus, it is necessary to send signals to the driver seat side, passenger seat side, and the like, and so a plurality of independent electrical signals may be output in some cases. There exists two possible methods for this: (i) dividing the acquired electrical signal, and (ii) using two or more devices. However, the first method requires a transistor and constant-current circuit as an accessory system, resulting in complexity and high cost. In the second method, cost is not only at least doubled, but it is difficult to obtain electrical signals having identical characteristics. Therefore, problems exist with either method.
In addition, in a case where a casing of an acceleration detecting device is formed with resin material, assembly performance during press-fitting is poor. In particular, there is a problem in which damage such as splitting of the cover occurs in the case of press-fitting with the cover remaining tilted.